Surgical staplers have found wide-spread acceptance in surgical procedures since such devices drastically reduce the amount of time required by surgeons to suture body tissue.
Typically, such surgical staplers have a pair of upper and lower jaw members to clamp body tissue therebetween. The lower jaw member typically carries a staple cartridge which contains a plurality of staple drive members having cam contact surfaces in association with one or more laterally spaced rows of surgical staples. The upper jaw member has an anvil portion to close the surgical staples which have passed through body tissue. The stapler is further provided with at least one pusher bar longitudinally moveable relative to the jaw members and having a cam surface for engaging the cam contact surfaces of the staple drive members so that the longitudinal movement of the pusher bar sequentially drives the staple drive members, through a camming action, to fire surgical staples from the cartridge.
For some uses, double-row stapling is preferable to single-row stapling in providing secure hemostasis. Accordingly, some currently available surgical staplers include double staple drive members respectively formed of a single piece construction having two staple driving surfaces for firing two rows of surgical staples. These double staple drive members are longitudinally arranged in a row within the cartridge to be driven with a single stroke of the pusher bar. Typical arrangements include double staple drive members each having a longitudinally-staggered pair of staple driving surfaces which bridge the pusher bar path.
U.S. Pat. No. 4,978,049, to Green, discloses a modification which includes triple staple drive members respectively formed of a single piece construction having three laterally spaced staple driving surfaces capable of firing three rows of surgical staples. However, this arrangement has distinct disadvantages.
As the number of the staple driving surfaces for firing individual staples increases, greater resistance is created to the longitudinal movement of pusher bar. This requires a surgeon to apply a greater force in operating the surgical stapler. Furthermore, there can be a tendency for the staple drive members to bind against the walls of cartridge slots and jam due to an unbalanced force distribution applied to staple driving surfaces.
Therefore, it is highly desirable to design and arrange the pattern of individual staple drive members and driving surfaces to facilitate application of the driving force by the surgeon throughout the pusher bar stroke to provide a surgical stapler which allows a smooth stapling operation.